Fibroblast cell lines have been used as supporting cells for the growth of other cells for decades. The fibroblast cell lines generally used for this purpose are 3T3 cells and MEF cells. The 3T3 cell line was first described in 1963 (Todaro, G. J. and Green, H., 1963, J. Cell Biol., 17:299-313). The 3T3 cell line is an immortalized fibroblast cell line derived from mouse embryos 17 to 19 days old. The 3T3 cell line, however, is not suitable for growing and maintaining pluripotency of embryonic stem cells.
More recently, a source of supporting cells was described, freshly derived mouse embryonic fibroblasts (MEFs) (Robertson, E. J., 1987, Embryo-derived stem cell lines, Teratocarcinomas and Embryonic Stem Cells: A Practical Approach, E. J. Robertson, Oxford, UK, IRL Press). The MEF cell line is derived from mouse embryos 13-14 days old and is not an immortalized cell line. The MEF cell line, unlike 3T3 cells, can be used for growing and maintaining the pluripotency of embryonic stem cells. MEF supporting cells have become the standard for growing and maintaining embryonic stem cells in serum free media. These fibroblasts, however, have drawbacks including a short lifetime in culture and the need for repeated isolation.
A need exists for an immortalized fibroblast cell line that has at least the embryonic supporting properties of MEF cells.